The present invention relates to an eyeglass frame shape measurement apparatus which traces a groove of a rime of an eyeglass frame and measures the three-dimensional shape of the rim.
Various eyeglass frame shape measurement apparatuses are known in which a tracing stylus is pressed and inserted into the groove of a rim of an eyeglass frame held by an eyeglass frame holding mechanism, and a position of the tracing stylus which moves to follow changes in the rim is detected to obtain a three-dimensional shape of the rim in a moving radius direction (XY direction) and a direction perpendicular to the moving radius direction (Z direction) (for example, see JP-A-2000-314617 (U.S. Pat. No. 6,325,700), JP-A-2001-174252, JP-A-2006-350264 (U.S. Pat. No. 7,571,545), JP-A-2009-14517 (U.S. Pat. No. 7,681,321)).
As shown in FIG. 14, a measurement mechanism of this type of apparatus includes a rotation base RB which rotates with respect to a rim FW, a tracing stylus shaft SA which has a tracing stylus ST attached to an upper end thereof, a moving base VB which movably holds the tracing stylus shaft SA in a vertical direction (Z direction) and is provided in the rotation base RB to be movable in a moving radius direction passing through the rotation center CO of the rotation base RB, and an urging mechanism which urges the moving base VB toward the rim FW so as to generate a measurement pressure for pressing the tracing stylus ST into the groove of the rim FW. The tracing stylus ST moves to follow changes in the rim on the basis of the rotation of the rotation base RB, and the movement of the tracing stylus ST at that time is detected. Thus, the three-dimensional shape of the rim is measured.
In recent years, an eyeglass frame in which the rim has a large curvature is increasingly used. Thus, a tracing stylus having a needle-like tip end is used.